Embossing gear for foil or other material



c. T. HALL EMBOSSING GEAR FOR FOIL OR OTHER MATERIAL Filed July 24, 1951 Sept. 25, 1956 3 Sheets-Sheet l 1 HWENTOR (Z. J. Hafiz M Mv-m I ATIO/P/VEYS C. T. HALL Sept. 25, 1956 v EMBOSSING GEAR FOR FOIL OR OTHER MATERIAL 3 Sheets-Shea.

Filed July 24, 1951 .mnwro/P Na 7 A roENEYS Sept. 25, 1956 c. T. HALL 2,763,893

EMBOSSING GEAR FOR FOIL. OR OTHER MATERIAL Filed July 24, 1951 3 Sheets-Sheet 5 nited States EMBOSSING GEAR Fon FOIL oR o En MATERIAL Charles Thomas Hail, Deptford, London, Engiand, as-v signor to Molins Machine Company Limited, London, England, a British company This invention concerns improvements in or relating to embossing gear for foil or other material.

On packing, wrapping and like machines there is often incorporated a device for embossing the metal foil or other wrapping material. Such a device is referred to herein as an embossing gear.

T he present invention is concerned with such embossing gears, but it should be understood that it is not restricted in its application to any particular type of machine or material.

On cigarette packing machines, for example, the wrapping material is often paper-backed metal foil, particularly aluminium foil, and on such a machine a known form of embossing gear comprises two parallel rotating rollers pressed one against the other, one being of steel, upon which the pattern or design is engraved or formed, the other having a rubber-covered circumference which, when foil is passed between the rollers, presses the foil against the steel roller. The results from this arrangement are not very satisfactory however because a sharp impression not obtained on the foil, for the rubber, although deformed by the pressure of the steel roller, does not form the definite counterpart to the steel roller which is essential for good impressions on foil and like materials.

Another known type of embossing gear comprises two rotating rollers in a similar arrangement to that described above, one of the rollers being made of steel and the other of compressed paper. This latter consists usually of a very large number of paper discs compressed axially on a mandrel, the circumference being ground to size. When being prepared for embossing purposes it is run at normal operating speed in engagement, under great pressure, with the steel roller for approximately 8 hours, the surface of the paper roller being continually softened by application of a soap solution whereby a de sign which has previously been formed on the steel roller is repeated on the paper roller which then constitutes a mating roller to the steel roller. The rollers are geared together and when foil is passed between them, the impression of the rollers is imparted to the-foil. This arrangement gives very satisfactory embossing when the paper roller is new, but these rollers are extremely expensive. Good paper rollers will last several months but they are subject to irregular wear and are easily damaged. For example, the paper roller may be damaged by a piece of card or a piece of string passing between the rollers. Moreover, the paper roller soon loses its sharply defined impression and foreign matter has a tendency to adhere to and clog the roller.

For this purpose a mating roller is prepared, in a manner more fully described hereafter, of .a zthermoplastic material such as a cellulose ether or ester, :21 polystyrene, a polyvinyl resin, a polyamide resin (e. g. nylon) and especially a polyacrylic resin (e. g. polymethacrylic ester). Any such thermoplastic material appears to be satisfactory, the essential requirement being that the .material should have sufiicient solidity at operating tematcnt 'ice peratures. Such a material will be termed hereafter thermoplastic material or plastic.

The surface of the mating roller is prepared by impression from a metal co-operating roller, which is usually the pattern roller used in the embossing gear and is referred to hereafter as a pattern roller. Among the acrylics is the well known polymethyl methacrylate, described under the heading, Acrylic Resins," in the 1945 Encyclopedia of Plastics, Plastics Catalog Corp., New York, N. Y., beginning on page 160, and the specific description following relates to the preparation of a roller from this particular material. Thermoplastic material, as defined above, is fairly hard, though easily machined and after being deformed while being subjected to heat will, on a subsequent reheating revert to its original shape, that is the shape possessed prior to the deforming operation. When heated it will take a sharp clear impression from a die and if the heat is a slightly more intense or more prolonged, than is absolutely essential, sharp edges of the impression tend to become blunter, that is, the material flows slightly under the heat and so a sharp-cornered edge changes to a curve of small radius. The heating also tends to make the surface of a glass-like smoothness and particles of paper, foil, orthe like do not easily cling to such a surface. Heating to this degree is called hereafter the desired amount of heat. As sold, the material may shrink on cooling after being heated for the first time, and so to provide for this, the material from which the roller is to be made is heated and cooled, and thereafter subsequent heating does not affect the final dimensions. This preliminary heating is known as mor malising.

The present invention provides a method of and apparatus for making a mating roller of plastic wherein the mating roller has its embossed surface formed by running it in contact with a pattern roller and pressing and running the surfaces of the two rollers together whilst applying the desired amount of heat to successive portions of the surface of the mating roller at the region of Contact. The invention further comprises a mating roller of thermoplastic material, as herein defined, for use in such a gear, whose embossed surface is formed as S 1 forth above. The roller may comprise a sleeve of said material fixed on a suitable spindle.

Further according to the present invention there is pro: vided an embossing gear having a roller (.e. g. of metal) bearing a pattern and a mating roller, made by the method set forth above, which is geared to rotate with the roller bearing the pattern.

A method of producing a mating roller according to the invention will now be described with reference to the accompanying drawings, which show by way of example a foil embossing gear for a sigarette packing machine.

In the drawings:

Figure l is a front elevation of an embossing gear.

Figure 2 is a sectional plan of Figure 1.

Figure 3 is a side elevation of a simple machine on which the rollers are embossed.

Figure 4 is an end elevation of Figure 3.

Referring first to Figures 1 and 2 the general construction of such a gear is well known andcomprises a parallel pair of horizontal embossing :rollers 1 and 2 supported in bearings 3 and 4 in a frame 5 and urged together by springs 6. Pressure is applied or released by a hand lever 7, the precise arrangement being described in more detail later. Foil wound upon a reel disposed above the rollers is passed bet-ween them for embossing.

In the particular construction now described the roller 2 is made of a hardened steel, and preferably an alloy tee c n a n h m m, ybdenum, nd alum num (The Condensed Chemical Dictionary, 1930 edition, pub

lished by The Chemical Catalog Company, Inc., New York, N. Y., page 330, column 2) which has an extremely hard surface and does not distort appreciably when subjected to heat. This roller is engraved with the desired pattern. The other roller generally indicated by the reference 1 comprises a steel mandrel 8 having a sleeve 9 on it made of an acrylic, hereafter for brevity, simply termed plastic. This may be of an approximate thickness of A which thickness is suitable for making a composite roller of approximately 4" diameter x 5" long, the roller being substantially the same length as the steel roller and exactly twice the diameter. The diameters given of course relate to a particular length of blank to be embossed.

The two rollers are geared to one another by spur gears 14 and and the steel roller 2 makes two revolutions to one of the plastic roller 1.

A cover consisting of a fixed part 10 and a hinged part 11 is provided to protect the rollers from abuse, as by permitting hard objects to fall on to them. The cover 11 is slidable and fixed by a screw 12 to close the gap between the parts of the cover to a minimum. A bracket 13, Figure 1, shown in chain lines will be referred to later.

Reference is now directed to Figures 3 and 4.

For the purpose of preparing the plastic roller for embossing purposes the gear above described is removed from the machine and mounted in a simple machine, shown in Figures 3 and 4, with the plastic roller 1 vertically disposed above the steel roller 2. The steel roller has been engraved as usual with a required design and the plastic roller has been at this stage normalised by heat treatment to relieve it of stress, and turned and polished to its correct diameter.

The machine shown in Figures 3 and 4 consists of a tubular stand 16 shaped as shown and having a table or plate 17 at its top. The bracket 13 shown in Figure l (which is not part of the packing machine but is fixed to the embossing gear in the same way as a support bracket on the packing machine) is bolted to the table as shown in Figure 3 so that the gear is now in the desired position. On a platform 18 fixed to the stand 16 is a motor 19 which drives a compressor 20 to supply air to a gas torch 21. From the motor is a drive by belt 22 to a gear box 23 which drives a small sprocket wheel 24. A chain 25 running on this sprocket wheel drives the steel roller 2 which has a sprocket wheel 26 fixed to its spindle 28 for this purpose. The spindle can also be rotated by a hand crank 27 which may be detached when the spindle is driven by power. The bracket 13 supporting the embossing gear also provides a fixing for a guard plate 29 which is adjusted parallel to and very close to the steel roller at a position just after the line of contact of the two rollers, when considered relative to the direction of rotation of the rollers.

Referring again to Figures 1 and 2, the bearings 3 of the plastic roller are slidable in the frame 5 of the embossing gear and light springs 30 tend to urge this roller away from the steel roller. A spindle 31 provided with cams 32 positioned behind the slidable bearings 3 has the lever 7 fastened to one end. As seen from Figure 2 the cams are eccentric to the spindle axis. This arrangment provides a rapid method of closing and separating the rollers. The cam spindle is in turn supported in a sliding member or bridge 33 and is spring urged towards the rollers by the springs 6, this springing providing a resilient operating pressure on the rollers which will yield if foreign bodies pass by accident between the rollers.

In practice the depth of the impression on the plastic roller may only be about 0.001" so that if the two rollers are out of parallelism by half of this the effect on the embossed foil is quite noticeable. The bridge 33 is able to float on the springs 6 and these urge the plastic roller against the steel roller so that it mates properly and is truly parallel therewith. Once the cam movement has brought the rollers into proper contact any further movement of the cams merely causes the bridge 33 to move away from the roller against the pressure of the springs.

When the embossing gear is placed in the machine, Figures 3 and 4, the rollers are separated by the cams. The gear is connected to the motor which gives a final speed of 1 revolution per minute through the gear box, with a one to three reduction by the chain drive which results in the steel roller being driven l revolution every 3 minutes.

A flame from the torch 21 is played upon that part of the steel roller lying underneath the guard 29. The torch is moved to and fro by an operator. Rotation of the roller results in the even heating of same, the guard serving to protect the plastic roller from the flame.

A surface pyrometer 34 shown diagrammatically which will quickly detect a temperature change is used to detect the surface temperature of the roller and is applied to a position just before the line of contact of the rollers.

When the pyrometer shows a temperature of 120 the plastic roller is urged gently towards the steel roller by the cams to which reference has previously been made, and the two rollers are permitted to rotate together, the plastic roller making 2 revolutions before it is slowly withdrawn from contact with the steel roller. During this period of contact of the two rollers the flame is adjusted to keep the pyrometer temperature readings between C. and C., this range of temperature having been found to be suitable. Temperatures lower than 115 C. result in the plastic being too firm to receive a good impression from the steel roller whereas temperatures above 120 C. cause the plastic to become too fluid and the impression of the steel roller tends to vanish as the material seeks to return to its original shape.

After the separation of the rollers, the plastic roller is allowed to make one complete revolution during which time it cools to approximately 70 C. and is then ready for use.

Using this method the heat is applied to the plastic in such a fashion that only very local softening results and the plastic is firm almost immediately after contact with the steel roller. The whole process may be performed in half an hour or so. The resulting surface of the plastic is extremely smooth and proves very satisfactory, for there is little or no tendency for foreign matter to adhere to its surface and consequently is very clean and clear in use. Furthermore, in the process of the heat treatment after the plastic ceases to contact with the steel roller, sharp corners in the plastic become converted into curves of very small radius which are very desirable, as no rough sharp edges exist to cause tearing of the embossed material.

When using paper rollers, great operating pressures are required when embossing, due to the paper yielding. Owing to the comparatively solid nature of the plastic used only relatively light operating pressures are required. On the cigarette packing machine in question many years of life may be obtained from one of these rollers and it is only necessary to renovate it approximately every three months to maintain good results. It is necessary to run in a paper roller every week and this roller has a life of only one year, and the results from the latter part of this life are very poor owing to deterioration in the operative surface, which becomes very pitted.

When run with a steel roller the plastic roller still remains clean and free from foreign bodies even though the steel roller may get quite clogged.

It will be appreciated that in some constructions it may be possible to run two plastic rollers together, both being made and renovated by two master steel rollers.

It is convenient for a mating pair of rollers to be marked to ensure correct matching up the pair so that the designs coincide.

What I claim as my invention and desire to secure by Letters Patent is:

1. Apparatus for forming, on a thermoplastic operative surface of a mating roller, an embossed pattern matching a pattern on the surface of a metal pattern roller, whereby the two said rollers can cooperate to emboss said pattern on flexible material such as metal foil passed between them, comprising a metal pattern roller Whose operative surface has the desired pattern engraved thereon, means to mount the said pattern roller for rotation, a mating roller having a smooth ther elastic operative surface consisting of a thermoplastic r aterial that has the characteristic of tending to revert to its original shape by flowing after being deformed while being heated, means to mount the mating roller for rotation with its operative surface in contact with that of the pattern roller, means to press said contacting surfaces against each other, means to rotate said rollers together while said contacting surfaces are pressed against each other, and heating means to apply heat to the surface of the pattern roller at a position remote from that at which the surfaces of the two rollers make contact, whereby heat is transferred by the pattern roller to the mating roller only during contact between their surfaces.

2. A method of making a mating roller on whose surface is impressed an embossed pattern and which can cooperate with an embossing roller, having a correspondingly patterned surface, to impress said pattern on flexible material such as metal foil passed between the two rollers, which method comprises the steps of forming a roller having a smooth thermoplastic surface consisting of a thermoplastic material that has the characteristic of tending to revert to its original shape by flowing after being deformed while being heated, pressing said surface against the patterned surface of an embossing pattern roller, and rolling said thermoplastic surface on said patterned surface while applying to the said thermoplastic surface, at only that region of said surface which at the moment is in contact with said pattern surface, sufficient heat to cause the thermoplastic surface while in such contact to have impressed thereon the pattern on the contracting part of said patterned surface, and to cause the material, immediately after such contact has ceased, to flow only to such an extent that the impression retained on said thermoplastic surface is slightly less sharp than the impression originally formed thereon by the said pattern surface.

3. A method of making a mating roller on whose surface is impressed an embossed pattern and which can cooperate with an embossing roller, having a correspondingly patterned surface, to impress said pattern on flexible material such as metal foil passed between the two rollers, which method comprises the steps of forming a roller having a smooth thermoplastic surface consisting of an acrylic resin that has the characteristic of tending to revert to its original shape by flowing after being deformed while being heated, pressing said surface against the patterned surface of an embossing pattern roller, and rolling said thermoplastic surface on said patterned surface while applying to the said thermoplastic surface, at only that region of said surface which at the moment is in contact with said patterned surface, sufiicient heat to cause the thermoplastic surface while in such contact to have impressed thereon the pattern on the contacting part of said patterned surface, and to cause the material, immediately after such contact has ceased, to flow only to such an extent that the impression retained on said thermoplastic surface is slightly less sharp than the impression originally formed thereon by the said pattern surface.

4. A method of making a mating roller on whose surface is impressed an embossed pattern and which can crate with an embossing roller, having a correspondingly patterned surface, to impress said pattern on flexible material such as metal foil passed between the two rollers, which method comprises the steps of forming a roller having a smooth thermoplastic surface consisting of a thermoplastic material that has the characteristic of tending to revert to its original shape by flowing after being deformed while being heated, rolling said surface on the patterned surface of an embossing pattern roller while pressing the two surfaces together and while applying to the said thermoplastic surface, at only that region which at the moment is in contact with said patterned surface, suflicient heat to cause the thermoplastic surface while in such contact to have impressed thereon the pattern on the contacting part of said patterned surface, and causing that part of said thermoplastic surface which has just moved out of such contact to be sufliciently heated to cause the material in that part to flow only to such an extent that the impression retained on said thermoplastic surface is slightly less sharp than the impression originally formed thereon by the said pattern surface.

5. A method of making a mating roller on whose surface is impressed an embossed pattern and which can cooperate with an embossing roller, having 9. correspondingly patterned surface, to impress said pattern on flexible material such as metal foil passed between the two rollers, which method comprises the steps of forming a roller having a smooth thermoplastic surface of polymethyl methacrylate, pressing said surface against the patterned surface of a steel embossing patterned roller, and rolling said thermoplastic surface on said patterned surface while heating said patterned surface and maintaining it at a temperature of between C. and C. at the region of contact between the two rollers.

References Cited in the file of this patent UNITED STATES PATENTS Re. 16,384 McCrohan July 13, 1926 53,920 Halsey Apr. 10, 1866 366,755 Baker July 19, 1887 683,893 Baron Oct. 8, 1901 1,454,243 Mclndoe May 8, 1923 1,659,371 Merrill Feb. 14, 1928 1,822,538 Neidich Sept. 8, 1931 2,060,828 Schultz Nov. 17, 1936 2,073,209 Heitman Mar. 9, 1937 2,193,899 Casto Mar. 19, 1940 2,232,551 Merton Feb. 18, 1941 2,406,718 Thomas Aug. 27, 1946 2,464,082 Hart Mar. 8, 1949 

